1. Field of the Invention
The invention relates to digital signal processing, particularly to electronic image processing of video signals to provide spatial and/or temporal scaling.
2. Description of Background Art
Various video formats are currently in use, depending on the particular source of the video signal. For example, video output dimensions are defined one way for conventional television screens and yet other dimensions for cinema or movie theater presentation. Furthermore, video recording format varies significantly between U.S. and European standards (i.e., PAL vs. NTSC). Additionally, video signals are transmitted using different frame rates when displayed on computer screens, as opposed to television screens.
Conventionally, video output is scaled spatially, i.e., horizontally and/or vertically, to desired dimensions by simple window-cropping, direct decimation, or direct repetition. However, such conventional techniques tend to cause loss of viewing information or introduce annoying viewing artifacts. In the prior art, there are number of filtering techniques that address such issue. For example, see: U.S. Pat. No. 5,574,572 to Malinowski et al. which describes time-invariant, spatial scaling for progressive-scan video; U.S. Pat. No. 5,621,870 to Shyu et al. which describes uniform spatial scaling for progressive-scan video; U.S. Pat. No. 5,089,893 to Iwase et al. which describes spatial picture element number converter for interlaced video; U.S. Pat. No. 5,283,651 to Ishizuka et al. which describes spatial scaling for interlaced video; and U.S. Pat. No. 5,384,904, to Sprague et al. which describes spatial scaling for progressive scan video.
Such conventional video scaling techniques tend to be quite complicated to implement, often requiring substantial amounts of storage and arithmetic processing. Hence, there is a need to provide improved technique for formatting video signals in much more efficient manner. In particular, it is desirable to scale the video input signal to certain output signal having certain spatial as well as temporal formats.